The facade system consists of an outer, sintered—and therefore waterproof—structure into which modular inner elements can be inserted. Through a drip system and strategically placed recesses in the modules’ pressure path, water is channeled vertically through the structure and distributed to humidify the inner modules. Once the facade is saturated, the system can be paused or the excess water can be returned to a reservoir.

In a series of experiments, the vertically aligned layer orientation demonstrated the most uniform distribution of moisture within the modules. Due to capillary action in the pores of the clay, the water can also spread to a limited extent against gravity, which promotes homogeneous moisture penetration throughout the structure.

The ribs of the inlays and the textured surface create an increased surface area. As the surface area increases, so does the evaporation potential and, consequently, the evaporation rate. In addition, the continuous humidification of the modules enables the use of epiphytic plants, such as tillandsias, which are characterized by their low maintenance and water requirements.

The degree of opacity of the facade can be flexibly controlled by the number and arrangement of the internal modules used.

Degrees of freedom are a way to define an object’s range of motion based on movements along and around the respective axes. This principle was used in the geometric design of the facade stones to create an interlocking pattern, as shown in the following diagram. The opposing curvatures prevent movement along both the X- and Z-axes. If the adjacent stones on either side of a panel are then clamped in place, this results in all stones being completely secured.

The requirement that the panels be individually installable and replaceable has resulted in five types of cladding blocks. A distinction must be made between the blocks located in the center of the panel and the edge blocks, which have a shallower curve to prevent interlocking with the next row.

All cladding blocks have recesses in their upper and lower surfaces to allow water to flow through. The cladding blocks have a wall thickness of 8 mm, consisting of a double-walled 4-mm structure. In testing, this design produced the best results in terms of dimensional stability under overhangs. For the cooling inserts, there is a version for both full blocks and half blocks.

The facade is divided into smaller modules that can be mounted directly onto a substructure. The edge stones of each panel are clamped into and secured within a perimeter frame. The interlocking of the individual stones stabilizes the entire module and holds it together through friction, without requiring additional mechanical fasteners within the surface.

While the sintered outer blocks are frost-resistant due to their low water absorption, the high porosity of the inner blocks—which is necessary for evaporative cooling—conflicts with frost resistance and poses a design challenge. Despite numerous frost tests yielding positive results, a key objective of the design process was therefore to design the insert bricks as easily replaceable elements to ensure the facade’s longevity and ease of maintenance even under changing climatic conditions.

To compensate for manufacturing tolerances resulting from material variations and shrinkage during the drying and firing processes, compensating joints are strategically placed between the dry-jointed bricks, enabling more uniform load distribution and reducing local stress peaks.

For the clay 3D printing process, commercially available fine-grained clay (0–0.2 mm) with a 25% fireclay content was used. To achieve the required plasticity, water was added to the clay and thoroughly kneaded into the mixture until homogeneous. The best printing results were achieved after an additional day of resting, as this promotes a more even distribution of water within the material.

Printing was performed using a WASP Delta 2040 printer. After the modules had dried for one to two weeks, they were ready for firing. The firing parameters for the insert modules differed significantly from those for the cladding bricks.

The cladding bricks were fired at higher temperatures to induce sintering, which makes them waterproof. The insert modules, on the other hand, were fired at lower temperatures to achieve increased porosity, which allows them to store water for evaporative cooling.

The geometry of the stones features significant overhangs, which initially led to the collapse and separation of the layered structure. By using weaving patterns created through the manipulation of path curves, more pronounced overhangs were achieved. A uniform shift of the control points in alternating directions, along with a normal intermediate layer every other level, proved to be the most effective approach.

To make the developed facade system more tangible, a case study was used. The building in question is an old, multi-story parking garage in the city center. It is located at Conrad-Adenauer-Straße 15 in Frankfurt am Main. Its open envelope makes it well-suited for the cooling system, as wind can flow through the facade elements.

In particular, the pedestrian zone adjacent to the ground floor offers significant potential for improving the local climate by creating a temperature-regulating buffer zone through the new facade structure.

This case study demonstrates how the targeted retrofitting of existing buildings can enhance not only the building itself but also the surrounding public space by sustainably improving the local microclimate.

At the same time, it serves as a representative example of the many old parking garages in our city centers that are in need of renovation and often no longer fit into the urban landscape.

In order to verify the implementation and feasibility of the thesis on a 1:1 scale and to be able to draw conclusions based on measurement data, a panel was constructed as a demonstrator.

It consists of a substructure, 21 full cladding blocks, 6 half cladding blocks, 14 cooling fin insert blocks, and an additional 6 half insert blocks.

In the next phase of the project, the cooling capacity of the structure will be tested, evaluated, and documented using the demonstrator. To do this, it will be placed in a controlled and temperature-regulated environment. Room temperatures and surface temperatures on the structure will be measured.

Supervision

Prof. Dr. -Ing. Oliver Tessmann

TT-Prof. Dr.- Ing. Christina Eisenbarth

Max Eschenbach Dipl. Des.

Acknowledgement

Many thanks to Prof. Oliver Tessmann and Prof. Christina Eisenbart for their helpful contributions and guidance on my thesis.

And a special thank you to Max Eschenbach, who not only shared his expertise but also provided emotional support and encouraged me.